AC/DC Machinery Reviewer PDF

AC/DC Machinery Reviewer - A 3 phase winding is placed in these slots and serves as the armature winding of the alternator Alternators Advantages of Stationary Armatu...

AC/DC Machinery Reviewer - A 3 phase winding is placed in these slots and serves as the armature winding of the alternator Alternators Advantages of Stationary Armature Alternating Current Generator ✓ The armature winding can be braced well, so AC generators as to prevent deformation caused by the high - Primary source of all energy we consume centrifugal force. - usually called ALTERNATORS ✓ It is easier to insulate stationary winding for - operates on the same fundamental principle of high voltages for which the alternators are electromagnetic induction as a dc generator usually designed. when the flux linking a conductor changes, an ✓ The high voltage output can be directly taken e.m.f. is induced in the conductor. out from the stationary armature. Whereas, for a - operates in a very definite constant speed rotary armature, there will be large brush contact drop at higher voltages, also the sparking at the Alternator Construction brush surface will occur. Rotor & Stator Field windings are the windings ✓ Field exciter winding is placed in rotor and the producing the main magnetic field (rotor low dc voltage can be transferred safely. windings) Armature windings are the windings ✓ The low-voltage field can be constructed for where the main voltage is induced (stator efficient high speed operation windings) Armature Windings for Alternators Alternator Construction Armature windings are symmetrically Rotor The rotor of a synchronous machine is a distributed in slots around the complete large electromagnet. circumference of the armature - Carries a field winding which is supplied with direct current through two slip rings by a Ac machines are of 3-phase type, the three separate dc source windings of the three phases are identical but - DC source (called exciter) is generally a small spaced 120 electrical degrees. dc shunt or compound generator mounted on Armature windings may use full-pitch coils or the shaft fractional-pitch coils The field winding of an alternator is placed on Half-Coiled the rotor and is connected to d.c. supply through Half as many coils, each with twice as many two slip rings. turns, as in the whole-coiled arrangement, for the same phase voltage. Slip rings are metal rings completely encircling the shaft of a machine but insulated from it. Whole-Coiled Graphite-like carbon brushes connected to DC Twice as many coils, each with half as many terminals ride on each slip ring supplying DC turns, as in the half-coiled arrangement, for the voltage to field windings. same phase voltage Successive groups carry opposing current. Types of Rotor Frequency of alternators Salient Pole Rotor By the definition, synchronous generators - Is generally used for slow speed machines produce electricity whose frequency is having relatively large diameters and relatively synchronized with the mechanical rotational small axial lengths. - Water turbines are most speed. efficient when rotating at low speeds (200-300 rpm); therefore, they usually turn generators with Armature Windings for Alternators Armature many poles. Winding Coil pitch Non-Salient Pole (Cylindrical) - The distance between two sides of a coil Full- pitch coil Used for every high speed operation and - A coil with span of 180 electrical degrees employed in steam turbine driven alternators like Fractional-pitch coil turbo-generators. - A coil with span less than 180 electrical - Steam turbines are most efficient when rotating degrees at high speed; therefore, t o generate 60 Hz, they are usually rotating at 3600 rpm (2-pole). Advantages of Fractional-pitch Less copper is required per coil Stator - Built up of sheet-steel laminations (to The waveform of the generated voltage Is reduce losses due to eddy current) having slots improved on its inner periphery. Pitch Factor (Kp)  Fluorescent lamps The pitch factor (Kp) is the factor by which the Electromagnetic devices electromotive force (emf) is reduced in an Induction motor electrical machine. It accounts for the distribution of windings in the 3. Capacitive Load slots of the stator or rotor, affecting the overall A capacitive load charges and releases emf generated. energy. Capacitive reactance resists the change to voltage, causing the circuit current to lead Concentrated winding voltage - A winding with only one slot per pole per phase Capacitor devices - The emfs in the coils are in phase Synchronous motors - Phase difference is zero - The voltage generated per phase is equal to Alternator regulation the arithmetic sum of the individual coil volt age in that phase Character of the load RESISTIVE LOAD (UNITY POWER FACTOR) – Distributed winding 8% to 20% terminal voltage drop A winding with coils/phase is distributed over INDUCTIVE LOAD (LAGGING POWER several slots. FACTOR) – 25% to 50% terminal voltage drop The emfs in the coils are not in phase. CAPACITIVE LOAD (LEADING POWER Phase difference is not zero because the coils FACTOR) – terminal voltage will rise are displaced from each other by slot angle α. The voltage generated per phase is the phasor Terminal Voltage Behavior of Alternators sum of coil voltage. The terminal voltage will drop or rise will Distribution factor depend upon: - The factor that must be multiplied to obtain th e (1) the magnitude of the load correct value of generated voltage E (2) actual overall power factor of the combined - The distribution factor is less than 1, hence loads reduces the calculated voltage. In general, Slot angle –The greater the load, the greater will be the - Is the angular displacement in electrical drop or rise degrees between the adjacent slots –The lower the lagging power factor, the greater will be the voltage drop –The lower the leading power factor, the DISTRIBUTION FACTOR greater will be the voltage rise What is the effect of distribution the winding? – Distributing the winding in many slots has 2 Reasons when the load upon a dc shunt the effect of improving the shape of the voltage generator increases, the terminal voltage drops: wave: – By making it approach a sinusoidal function 1. The flux diminishes because of the effect – Adding rigidity and mechanical strength to of armature reaction and the fact that the field the winding voltage is reduced 2. a part of the generated voltage is used in Before an ac generator is ready to function to overcoming the resistance of the armature deliver electrical load: circuit. ✓ it must be brought up to synchronous speed by its prime mover 1. Armature-resistance Voltage Drop ✓ it must be separately excited from a dc source. - the current in a pure resistance circuit is in phase with the voltage required to cause that ✓ it must have its terminal voltage adjusted to current to flow through that resistance. the correct value by proper manipulation of the field rheostat. 2. Armature-reactance Voltage Drop - the current in a pure reactance circuit (one TYPES OF LOADS possessing inductance but no resistance) lags 1. Resistive Load by 90 electrical degrees behind the voltage Incandescent lamps required to cause that current to flow. Heating devices *inductance is a property of a conductor or Electric iron circuit that causes electromotive force generated Electric stoves by a change in current flowing Toasters and the like 2. Inductive Load 3. Armature-reaction Voltage Drop - the flux An inductive load converts current into a created by the armature current maybe said to magnetic field. Inductive reactance resists the develop a voltage that will vectorically add to or change to current, causing the circuit current to subtract from the generated voltage. lag voltage. Electric welders Simple steps to calculate alternator regulation Load cannot be shifted from one alternator to –The armature-resistance test another by field-current adjustment. –The open circuit test, and –The short-circuit test Hunting is a phenomenon where the rotors of Losses include with the alternator operating the two alternators swing forward and under load backward about the stable rotating positions. 1. Rotational Losses KEY TERMS Friction and windage - determined by using Alternator: A machine that generates a small auxillary motor to drive the unexcited alternating current (AC) electrical power. alternator at rated speed measuring the power Armature: The stationary part of an alternator input to the former. where the voltage is induced. Brush friction at the field collector rings - Armature Winding: The coils of wire wound where power is delivered to the field for around the armature core, carrying the induced excitation purposes, is quite small and is often current. neglected in the efficiency calculation. Coil Pitch: The angular distance between the Ventilation to cool the machine (if two sides of an armature coil. Distribution Factor: A factor accounting for the necessary) - power required to circulate air or voltage reduction due to the distribution of hydrogen and represents a loss chargeable to windings in multiple slots. the alternator. Exciter: A DC generator that provides the Hysteresis and eddy currents in the stator - current for the field windings of an alternator. determined by measuring the power input to an Field Winding: The windings on the rotor that auxillary motor with and without the field excited. create the magnetic field. Fractional-Pitch Coil: A coil spanning less than 2. Electrical Losses 180 electrical degrees. Field Winding - determined by multiplying the Frequency: The number of cycles per second of field-winding voltage by the field current, i.e., EF an alternating current, measured in Hertz (Hz). x IF. Inductive Load: A load that consumes reactive Armature Winding - calculated by the power and causes the current to lag behind the formula nIA2Ra voltage. Brush Contacts - between brushes and slip Non-Salient Pole Rotor: A smooth cylindrical rings, usually quite small and is often neglected rotor used in high-speed alternators. in the efficiency calculation. Paralleling: Connecting two or more alternators to operate together and share the load. 3. Losses in the exciter used for field Phase Sequence: The order in which the excitation - generally omitted from the efficiency voltages in a three-phase system reach their calculation and, are usually charged to plant peak values. operation. Power Factor: The ratio of real power (kW) to apparent power (kVA), representing the 4. Stray-Load Loss - they result from eddy efficiency of power utilization. currents in the armature copper conductors. Resistive Load: A load that consumes only real power and has the current in phase with the Terms that are needed to know voltage. Synchronizing - process of connecting one Salient Pole Rotor: A rotor with projecting poles machine in parallel with another machine or with used in low-speed alternators. an infinite bus-bar system. Slip Rings: Metal rings mounted on the rotor Running Machines – machine carrying load shaft to provide a connection for the DC Incoming Machine – the alternator which is to excitation current to the field windings. be connected in parallel with the system Synchronous Speed: The speed at which the rotating magnetic field of the alternator rotates, Conditions for Paralleling Alternator determined by the frequency and the number of poles. 1. The terminal voltage (r.m.s. value) of the Voltage Regulation: The change in terminal incoming alternator must be the same that as voltage from no-load to full-load conditions, busbar’s voltage. expressed as a percentage of the full-load 2. The frequency of the generated voltage of the voltage. incoming alternator must be equal to the Whole-Coiled Winding: An armature winding busbar’s frequency. where each coil spans 180 electrical degrees. 3. The phase of the incoming alternator voltage must be identical with the phase of the busbars SYNCHRONOUS MOTORS volt age. In other words, the two voltages must be in phase with each other. - Synchronous motors can develop a starting 4. The phase sequence of the voltage of the torque equal to the pull-out torque. incoming alternator should be the same as that of the busbars. - This means they can produce extremely high - Power Factor Operation: Can operate under a torque, sometimes reaching 300% or more of wide range of power factors (both lagging and their rated torque. leading), useful for power correction. - They are typically larger than induction motors, as smaller synchronous motors are more OPERATION OF A SYNCHRONOUS MOTOR expensive. - A 3-phase synchronous motor has two rotor poles (NR and SR) and stator poles (NS and ADVANTAGES OF SYNCHRONOUS MOTORS SS). Power Factor Control: The power factor can be - The stator winding creates a rotating field at easily controlled by adjusting the field current. synchronous speed. High Efficiency: Synchronous motors have very - The rotor is stationary until it reaches near high operating efficiency. synchronous speed, where it can then Constant Speed: They maintain a constant synchronize with speed under varying loads. the stator field. MOTOR CONSTRUCTION SYNCHRONOUS MOTOR IS NOT SELF- Windings STARTING - Whole coiled lap windings are placed in the - The rotor experiences alternating repulsion and slots of stationary laminated cores, similar to attraction from the stator poles, causing it to fail alternators for polyphase service. to start due to high inertia. Coil Composition - Large machines use multiple strands of copper DIFFERENT TORQUES OF A SYNCHRONOUS strips. MOTOR - Smaller motors use single strands. - Starting Torque: Torque developed when full voltage is applied to the stator; also known as Insulation Types breakaway torque. - Class A: Standard insulation, max temperature - Running Torque: Torque developed under 105°C. running conditions. - Class B: Capable of withstanding higher - Pull-in Torque: Torque at which the motor temperatures. pulls into step after starting as an induction motor (2-5% STATOR AND ROTOR below synchronous speed). Excitation of Rotor Windings - Pull-out Torque: Maximum torque without - Direct current excitation can come from an losing synchronism. exciting plant d-c system or a separate d-c generator. STARTING SYNCHRONOUS MOTOR - Standard excitation is typically 125 volts; 250- - To make the motor self-starting, a squirrel cage volt excitation uses wire-wound coils. winding (damper winding) is added to the rotor. - Motor-Generator Sets: Used for excitation in - The damper winding consists of copper bars low-speed synchronous motors short-circuited at the ends, forming a partial squirrel TYPES OF ROTOR FOR SYNCHRONOUS cage. MACHINES - Initially, a 3-phase supply is given to the stator Salient Pole Rotor while the rotor field winding is unenergized. - Features many projected poles mounted on a - The rotating stator field induces currents in the magnetic wheel. damper winding, allowing the motor to start as - Larger diameter, shorter axial length. an - Typically has 4 to 60 poles. induction motor. - Used in lower speed machines (100 to 1500 - Once the rotor reaches synchronous speed, it r.p.m). is excited by the d.c. source, creating poles that Non-Salient Pole (Cylindrical) Rotor attract the stator poles. - Cylindrical shape with parallel slots for rotor windings. APPLICATIONS - Smaller diameter, longer axial length. Synchronous motors are preferred for driving - Usually has 2 or 4 poles. high-power loads at low speeds, such as: - Used in high-speed machines (1500 to 3000 -Reciprocating pumps r.p.m). -Compressors -Crushers FEATURES OF A SYNCHRONOUS MOTOR -Rolling mills - Constant Speed: Runs at synchronous speed; -Pulp grinders speed can only change by varying supply frequency, given by N_s = 120f / P. KEY TERMS - Not Self-Starting: Must be brought to Alternator: An electrical generator that converts synchronous speed before synchronization with mechanical energy into alternating current (AC) the supply. electrical energy. Synchronous speed: The speed at which the REVOLVING FIELD rotating magnetic field of a synchronous motor - Three-phase windings create a resultant operates. It is directly proportional to the magnetic flux that rotates as if actual magnetic frequency of the AC power supply and inversely poles were being rotated mechanically. proportional to the number of poles in the motor. - The speed of the revolving field is directly Stator: The stationary part of an electric motor proportional to the frequency. or generator, which contains the windings that produce a magnetic field. ROTOR CONSTRUCTION Rotor: The rotating part of an electric motor or 1. Squirrel Cage: Made by forcing molten generator. conducting material into slots of a core. Salient pole rotor: A rotor with projecting poles 2. Wound Rotor: Used for speed control or that create a concentrated magnetic field. high starting torque Commonly used in lower-speed applications. Non-salient pole rotor (cylindrical rotor): A WHY DOES THE ROTOR ROTATE? smooth cylindrical rotor with slots for windings. A rotating magnetic flux induces an Used in high-speed applications. electromotive force (e.m.f.) in the Excitation: The process of applying direct stationary rotor conductors. current (DC) to the rotor winding of a The induced e.m.f. causes rotor current, synchronous motor to create a magnetic field. which opposes the cause of its production Damper winding (squirrel cage winding): A (Lenz’s law). set of conductive bars embedded in the rotor The rotor moves in the same direction as poles, short-circuited at the ends, which help in the flux to reduce relative speed. starting the synchronous motor and reducing oscillations. SLIP AND ROTOR SPEED Torque angle: The angular displacement Slip Speed: The difference between between the rotating magnetic field of the stator synchronous speed and actual rotor and the magnetic field of the rotor. speed. Hunting: An undesirable oscillation of the rotor Slip indicates how much the rotor 'slips around its synchronous speed. back' from synchronism. Synchronous condenser: An over-excited Slip is essential for inducing e.m.f. and synchronous motor operated without a load, generating torque. used to improve power factor correction. Power factor: The ratio of real power to Synchronous Speed: The speed at which the apparent power in an AC circuit. A higher power magnetic field rotates in the stator. factor indicates a more efficient use of electrical energy. Slip: The difference between synchronous Reluctance: The opposition of a magnetic speed and rotor speed circuit to the flow of magnetic flux. The revolving flux rotates synchronously relative to the stator but at slip speed relative to the rotor INDUCTION MOTOR FUNDAMENTALS AND APPLICATIONS ROTOR TORQUE Torque: The force that causes rotation, usually - Induction motors work similarly to transformers, measured in pound-feet. where the rotor receives power inductively. - As the load increases, the motor's speed - They can be viewed as rotating transformers decreases, leading to increased slip. with a stationary primary winding and a rotating secondary. Starting Torque: Torque developed at the - Polyphase induction motors are widely used in instant the motor starts. various industrial drives due to their efficiency - Can be greater or less than normal and reliability running torque. - Occurs when slip s is unity (100%). STATOR - - The stator has a 3-phase winding fed from a 3- REVERSE TORQUE (PLUGGING) phase supply. Reverse Torque: When torque is applied in the - The coils must be connected in series, opposite direction of the motor's rotation. producing a rotating magnetic flux at - This is often referred to as "plugging." synchronous speed given by: Function: It acts as a brake on the motor. N_s = (120F)/P where: INDUCTION MOTOR EFFICIENCY ( N_s ) = synchronous speed (RPM) Efficiency Losses: ( f ) = frequency (Hz) Copper losses in stator and rotor ( P ) = number of poles Iron losses (hysteresis and eddy current losses) Friction and windage losses in the rotor Efficiency Test 1. No Load Test: Total power = P_2 - P_1  2. Load Test: Total power = P_2 + P_1 KEY TERMS 3. Stator Resistance Test: Average resistance Air Gap: The space between the stator and between stator terminals, adjusted for phase rotor of an induction motor. resistance. Blocked Rotor Test: A test conducted on an induction motor to determine the rotor resistance Starting Induction Motors and reactance. Starting an induction motor is similar to a Dynamic Braking: A method of braking an transformer with a short-circuited induction motor by disconnecting it from the AC secondary, leading to high rotor current. supply and connecting the stator windings to a Important to minimize starting current to DC source. avoid voltage drops affecting other Efficiency: The ratio of output power to input equipment. power in an induction motor. Full-Load Torque: The torque developed by an INDUCTION MOTOR STARTING METHOD induction motor at its rated power output. 1. Full-Voltage Starting Induction Motor: An AC motor that operates on 2. Reduced-Voltage Starting: the principle of electromagnetic induction. o Reduced Voltage Compensation Lenz's Law: A fundamental law of Method electromagnetism stating that an induced o Reduced Voltage Line-Resistance current will flow in a direction that opposes the Method change in magnetic flux that produced it. 3. Part-Winding Starting Plugging: A method of braking an induction motor by reversing the phase sequence of the SPEED CONTROL OF INDUCTION MOTORS supply voltage. Polyphase: A system of AC power distribution Wound-Rotor Method: Effective for that uses multiple phases (typically three). motors up to about 500 hp. Revolving Magnetic Field: A magnetic field Concatenation Method: Two motors that rotates in space, produced by the drive a common load. interaction of polyphase currents flowing through Consequent-Pole Method: Connects stator windings. successive pole groups to produce Rotor: The rotating part of an induction motor. opposite polarity poles. Slip: The difference between the synchronous speed and the actual rotor speed, expressed as ELECTRIC BRAKING OF AC MOTORS a percentage of synchronous speed. Slip Rings: Metal rings mounted on the rotor Dynamic Braking: Stops the motor shaft of a wound-rotor induction motor, providing quickly by disconnecting the AC source. electrical connection to the rotor windings. - Smooth and accurate stops. Squirrel-Cage Rotor: A type of rotor Plugging: Involves interchanging two construction where the rotor conductors are bars stator leads to reverse the direction of the embedded in the rotor core and short-circuited revolving flux, stopping the motor quickly. at both ends by end rings. - Quick stop by reversing the motor's Stator: The stationary part of an induction motor. direction Synchronous Speed: The speed of the rotating magnetic field in an induction motor, determined Effects of Plugging by the supply frequency and the number of During the plugging period: poles in the stator winding. o The motor absorbs kinetic energy Torque: A twisting force that tends to produce from the load. rotation. o The speed of the motor decreases Wound-Rotor Motor: A type of induction motor as it works against the motion of where the rotor has insulated windings the load. connected to slip rings, allowing for external This process is essential for quickly resistance to be added to the rotor circuit. stopping or slowing down a motor-driven system. TRANSFORMER A transformer is a static device that Kinetic Energy Absorption: transforms electric power from one circuit o The motor takes in energy from the to another at the same frequency. moving load, reducing its speed. It changes a given input voltage to a Speed Reduction: different output voltage, which can be o The application of reverse torque either an increase or a decrease. leads to a decrease in the motor's speed. Purpose of Transformers: Electricity in power lines can exceed 300,000 volts, which is too high for direct use.  Transformers lower the voltage to make VOLTAGE TRANSFORMATION electricity usable for homes and The voltage ratio between primary and businesses. secondary coils is determined by the turns ratio. TRANSFORMER CONSTRUCTION Example: A transformer with a turns ratio Basic Components: of 25:1 can transform 12,000 volts to 480 o Two coils with mutual inductance. volts. o A laminated steel core. Coils: SLOW DEVELOPING FAULTS o Primary Winding: The coil Common issues include: connected to the AC supply. o Insulation failure of windings o Secondary Winding: The coil o Core heating from which energy is drawn. o Fall of oil level due to leaky joints Core: These faults serve as protection against o Made of laminated transformer more severe faults such as: sheet steel to provide a continuous o Short circuits between phases magnetic path. o Faults in tap-changing equipment o Laminations vary in thickness o Surges (0.35 mm for 50 Hz, 0.5 mm for 25 Hz). BUCHHOLZ RELAY o High silicon content steel is used A protective device used in transformers to minimize hysteresis loss. to detect slow developing faults. Transformer Housing and Components TRANSFORMER CONSTRUCTION Tank: All transformer leads exit through suitable o Transformers are housed in metal bushings. tanks filled with insulating oil. Types of bushings: o The oil cools the coils and provides o Porcelain bushings for moderate insulation. voltages. Insulating Fluids: o Oil-filled or capacitor-type o Modern transformers use synthetic bushings for high voltage fluids (e.g., ASKARELS) that are installations. non-flammable. Conservator: TYPES OF TRANSFORMERS BY o A small tank at the top for oil CONSTRUCTION expansion and contraction due to 1. Core-Type Transformer temperature changes. o Windings surround a significant Breather: part of the core. o An air filter that allows air in and 2. Shell-Type Transformer out as the oil temperature changes, o Core surrounds a significant part of using silica gel to indicate moisture the windings. levels. o Advantage: Less leakage flux. Buchholz Relay: o A gas-activated relay that operates TYPES OF TRANSFORMERS BY COOLANT when gas formation occurs, 1. Ventilated Dry-Type Transformers providing protection against faults. o Cooled by natural air convection. o Used in places like schools and HOW TRANSFORMERS WORK hospitals to avoid hazards from Energy Conservation: burning oil or toxic gases. o Transformers do not create o Requires periodic maintenance electricity; they change voltage (dust removal). levels. 2. Oil Immersed Self-Cooled Transformer Electromagnetic Induction: o Oil temperature rises due to heat, o Based on two principles: causing circulation. 1. An electric current produces o Cools through natural convection a magnetic field. and conduction. 2. A changing magnetic field o Suitable for transformers rated up induces voltage in a coil. to 30 MVA. Operation: 3. Oil-Immersed Forced Air-Cooled o The primary winding is connected Transformer to an AC voltage source. o Core and coils are immersed in oil, o The magnetic field builds up and cooled by forced air. collapses, inducing voltage in the o Uses fans to increase cooling secondary winding. efficiency. o Suitable for transformers rated up to 60 MVA.  4. Oil-Immersed Water-Cooled Key Terms Transformer Alternating Current (AC): Electrical current that o Core and windings are immersed periodically reverses direction. in oil with circulating cold water. Ampere (A): The unit of measurement for o Heat is carried away by water. electrical current. o Suitable for large capacity Breather: An air filter that allows air in and out transformers (hundreds of MVA). as the oil temperature changes. 5. Oil-Immersed Force-Oil Cooled Buchholz Relay: A safety device used in Transformer transformers to detect internal faults by sensing o Cooling is achieved by forced oil gas buildup or oil level changes. circulation. Conservator: A cylindrical tank at the top for oil o Uses pumps and heat exchangers expansion and contraction. for efficient cooling. Core: The magnetically permeable material in a 6. Air-Blast Type Transformer transformer that provides a path for the o Not immersed in oil; housed in a magnetic flux. metal box with air blown through. Current: The flow of electric charge. o Suitable for voltages below 25,000 Eddy Current: Circulating currents induced in a V. conductor by a changing magnetic field. Electromagnetic Induction: The process of TYPES OF TRANSFORMER BY WINDING generating an electromotive force (voltage) in a 1. Step-Down Transformer conductor by a changing magnetic field. o Reduces primary voltage to a Electromotive Force (EMF): The electrical lower value. potential difference that drives current flow. o Used in distribution substations. Flux: The amount of magnetic field passing 2. Step-Up Transformer through a given area. o Raises primary voltage to a higher Frequency: The number of cycles per second of value. an alternating current. o Located at the output of generators. Hysteresis Loss: Energy loss in a magnetic material due to repeated magnetization and Applications of Transformers demagnetization. Enable long-distance power transmission. Impedance: The total opposition to current flow Economical transmission of electricity. in an AC circuit, comprising resistance and Minimize power loss. reactance. Isolate end users from high supply Insulating Oil: A dielectric fluid used in voltages. transformers for cooling and insulation purposes. Transformer's design allows for remote Laminated Core: A transformer core generation of electricity, shaping the constructed from thin, insulated steel sheets to power industry. reduce eddy current losses. Leakage Flux: Magnetic flux that does not link UNDERSTANDING IDEAL TRANSFORMERS both the primary and secondary windings of a AND LOADS transformer. Ideal Transformer Magnetizing Current: The component of the An ideal transformer is a theoretical excitation current that establishes the magnetic concept with no losses: field in the core. o Resistance of each winding is Mutual Inductance: The property whereby a negligible. changing current in one coil induces a voltage in o The core is highly permeable, a nearby coil. requiring minimal magnetomotive Primary Winding: The winding of a transformer force (mmf) to establish flux. that is connected to the input voltage source. o No eddy-current or hysteresis Secondary Winding: The winding of a losses occur. transformer that is connected to the load. o All magnetic flux is confined within Step-Down Transformer: A transformer that the core. reduces voltage. Ideal transformers cannot be realized in practice Step-Up Transformer: A transformer that but serve as a starting point for understanding increases voltage. real transformers. Transformer: A static electrical device that transfers electrical energy between two or more Ideal Transformer Characteristics circuits through electromagnetic induction. Induced EMFs: In phase with each other. Turns Ratio: The ratio of the number of turns in Terminal Voltages: Also, in phase. the primary winding to the number of turns in the Currents: I_1 and I_2 must be in phase. secondary winding of a transformer. Voltage: The electrical potential difference between two points in a circuit.